| dc.description.abstract | Blast, caused by Magnaporthe oryzae, is the most destructive disease affecting finger millet [Eleusine coracana (L.) Gaertn. subsp. coracana], productivity in the world, however, genomic resources for elucidating on finger millet’s resistance to blast are not yet developed in Uganda. This study therefore assessed a selected panel of 190 diverse finger millet accessions comprising of landraces, introductions, breeding lines, and released varieties for responses to blast. Genomic regions associated with blast resistance were also identified through genome-wide association studies (GWAS).
The 190 accessions were screened at NaSARRI-Serere for three seasons under natural infection conditions out of which 129 accessions were genotyped using Diversity Arrays Technology (DArT) sequencing platform. Analysis of Variance (ANOVA) in GenStat version 22 determined phenotypic variability among accessions and across seasons for blast and selected agronomic traits. Broad sense heritability and correlations between pairs of traits were also computed in R statistical packages; whereas for GWAS analyses, Best Linear Unbiased Predictors (BLUPs) for individual seasons and combined seasons were derived using Meta-R version 6 statistical software and marker-trait associations were analyzed using TASSEL version 5.2.9 and a suite of R packages. Prior to GWAS analyses, Principal component analysis (PCA) and neighbor-joining (NJ) dendrograms to show relatedness among the 129 accessions were done in R packages using the 1,211 resultant high-quality SNPs.
GBK 029674A, Ikhululwe, and Okhale-1 were all resistant to leaf, neck, and finger blast. Ten (10) accessions were moderately resistant to blast with consistent higher yields across the three seasons. Both PCA and NJ dendrogram grouped the 129 accessions into three (3) clusters with the first three (3) PCs explaining 41.08% of observed genetic variation. Association mapping identified four (4) significant and thirteen (13) suggestive marker-trait associations (MTAs) located on chromosomes 1A, 4B, and 9B. Several candidate genes that are known to code for disease resistance proteins were identified in tight linkage disequilibrium with the significant SNPs including NB-ARC domain-containing proteins, Leucine rich repeats, Protein Tyrosine Kinases (PTKs) and Serine/Threonine Kinases (STKs), Chitinase class I enzymes; and Neprosin and Xylanase-containing proteins. The proteins identified above are variously constituents of pathogen recognition, signal transduction, biosynthesis of reactive oxygen species (ROS), and cell wall and membrane constituents such as cuticular waxes, triacylglycerols, phytoalexins, which are popular in biochemical and physical plant defense mechanisms against pathogens such as induced localized cell death and systemic acquired resistance (SAR). Since the for (4) significant SNPs identified in the current study are located on chromosomes previously reported to harbour blast resistance Quantitative Trait Loci (QTLs) and genes, these markers when converted into Kompetitive Allele Specific PCR (KASP) markers can be useful in routine applications for finger millet breeding against blast. The nine high yielding accessions with moderate resistance to blast (ACC 310, FMS 13-20, FMS 13-8, P 236, ABAO F, IE 6013, F7 SEC 220 x DR 33, FMS 13-12, and FMS 72) are potential variety releases after multi-locational and multi-seasonal trials for adaptability and market preferences. Robust KASP markers could also be developed based on SNPs identified, and validated for routine use in finger millet breeding programs | en_US |
